Induced-draft fan for hot air gun/air dryer

ABSTRACT

An induced-draft fan for hot air gun/air dryer includes a casing, the casing having a motor mount and a plurality of spiral wing guides radially arranged around the fan mount, a fan blade unit, and a fan motor mounted in the motor mount and controlled to rotate the fan blade unit, the fan blade unit having a semispherical body coupled to the fan motor, and a plurality of blades radially spirally arranged around the semispherical peripheral surface of the semispherical body, the blades being curved in direction reversed to the spiral wing guides, each blade having a top wind cut face and a bottom side edge disposed in flush with the bottom edge of the semispherical peripheral surface of the semispherical body.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to hot air guns/air dryers and, more specifically, to an induced-draft fan for hot air gun/air dryer.

[0002] A conventional fan for hot air gun/air dryer, as shown in FIGS. 1 and 2, is generally comprised of a casing B, a fan motor A mounted in the casing B at one side, and a fan blade unit C coupled to the output shaft of the fan motor A. When starting the fan motor A, the fan blade unit C is rotated to induced currents of air. This structure of fan is still not satisfactory in function, and has numerous drawbacks as outlined hereinafter.

[0003] 1. The fan blade unit C has a cylindrical profile with a smooth periphery. When rotating the fan blade unit C to induce currents of air, currents of air directly impact the smooth peripheral surface of the fan blade unit C, thereby producing much wind resistance that reduces the induced volume of currents of air

[0004] 2. Because the blades D of the fan blade unit C are radially extended from the smooth peripheral surface of the cylindrical body of the fan blade unit C, the fan blade unit C occupies much installation space. Increasing the size of the blades D in order to increase the capacity of the fan blade unit C simultaneously increase the dimensions of the fan blade unit C. In the limited space of the hot air gun/air dryer, the size of the fan blade unit C is limited.

[0005] 3. Because the body of the fan blade unit C has a cylindrical shape, much wind resistance is produced during rotary motion of the fan blade unit C, resulting in back turbulent flow of air and resonance noises.

SUMMARY OF THE INVENTION

[0006] It is one object of the present invention to provide an induced-draft fan for hot air gun/air dryer, which produces less wind resistance and turbulent flow of air. It is another object of the present invention to provide an induced-draft fan or hot air gun/air dryer, which induces a big volume of wind when operated. It is still another object of the present invention to provide an induced-draft fan for hot air gun/air dryer, which produces little noise during operation. According to one aspect of the present invention, the fan blade unit comprises a semispherical body, and a plurality of blades spirally radially arranged around the semispherical peripheral surface of the semispherical body and turned with the semispherical body to induce currents of air without causing much wind resistance. According to another aspect of the present invention, the casing of the induced-draft fan comprises a plurality of spiral wing guides radially arranged around the motor mount, which supports the fan motor. The spiral wing guides are curved in direction reversed to the radially spirally arranged blades of the fan blade unit, for causing induced currents of air to form an eddy blow of air.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]FIG. 1 is an exploded view of a fan for hot air gun/air dryer according to the prior art.

[0008]FIG. 2 illustrates the path of induced currents of air according to the prior art.

[0009]FIG. 3 is an exploded view of an induced-draft fan for hot air gun/air dryer according to the present invention.

[0010]FIG. 4 illustrates the path of induced currents of air according to the present invention.

[0011]FIG. 5 is a side view in an enlarged scale of the fan blade unit according to the present invention.

[0012]FIG. 6 is an applied view of the present invention, showing the induced-draft fan installed in a hot air gun.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0013] Referring to FIGS. 3 and 4, an induced-draft fan for hot air gun/air dryer in accordance with the present invention is shown comprised of a casing 1, a fan motor 2, and a fan blade unit 3. The casing 1 comprises a motor mount 11 on the inside at the center, and a plurality of wind guides 12 radially connected between the periphery of the motor mount 111 and the inside wall of the casing 1. The fan motor 2 is mounted in the motor mount 11 inside the casing 1. The fan blade unit 3 is coupled to the motor shaft 21 of the fan motor 2.

[0014] Referring to FIGS. S and 6 and FIGS. 3 and 4 again, the fan blade unit 3 comprises a body 31 and a plurality of blades 32. The body 31 has a semispherical profile and a center-mounting rod 311 disposed on the inside. The blades 32 are radially spirally arranged around the semispherical peripheral surface of the body 31, each having a top wind cut face 321 and a bottom side edge disposed in flush with the bottom edge of the semispherical peripheral surface of the body 31. After installation of the fan motor 2 in the motor mount 11 inside the casing 1, the fan blade unit 3 is inserted into the casing 1 to force the center-mounting rod 311 of the semispherical body 31 of the fan blade unit 3 into engagement with the motor shaft 21 of the fan motor 2. When starting the fan motor 2, induced currents of air are smoothly guided forwards through the semispherical peripheral surface of the semispherical body 31. Because the blades 32 are radially spirally arranged around the semispherical peripheral surface of the semispherical body 31, less wind resistance and turbulent flow of air is produced during the operation of the induced-draft fan. Because the wind cut face 321 cuts through the induced currents of air at a small angle, low noise is produced when currents of air are induced and guided out of the hot air gun 4 in which the induced-draft fan is installed.

[0015] Referring to FIG. 5 again, the wing guides 12 are spirally curved in direction reversed to the curving direction of the blades 32 of the fan blade unit 3. When rotating the fan blade unit 3 to induce currents of air, the spirally curved wing guides 12 guide the induced currents of air forwards, forming an eddy flow of air.

[0016] A prototype of induced-draft fan has been constructed with the features of FIGS. 3 and 4. The induced-draft fan functions smoothly to provide all of the features discussed earlier.

[0017] Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims. 

What the invention claimed is:
 1. An induced-draft fan for hot air gun/air dryer comprising a casing, a fan motor mounted in said casing, said fan motor comprising a motor shaft, and a fan blade unit coupled to said motor shaft of said fan motor and driven to induce currents of air upon operation of said fan motor, wherein said fan blade unit comprises a semispherical body coupled to said motor shaft of said fan motor, said semispherical body having a semispherical peripheral surface and a bottom edge, and a plurality of blades radially spirally arranged around the semispherical peripheral surface of said semispherical body, said blades each having a top wind cut face and a bottom side edge disposed in flush with the bottom edge of the semispherical peripheral surface of said semispherical body.
 2. The induced-draft fan of claim 1 wherein said casing comprises a cylindrical peripheral wall, a motor mount suspended inside said cylindrical peripheral wall and adapted to hold said fan motor, and a plurality of wing guides radially connected between said motor mount and said cylindrical peripheral wall, said wing guides being spirally curved in direction reversed to said blades of said fan blade unit. 